VS2005, ASP.NET, C#, IIS6
Hello friends,
I have a master page divided into three sections i.e. header, details, footer.
The header section contains web user control having AJAX tab container. We are showing or hiding tabs according to user previleges. Initially only one tab is active showing user to log in. When the user logs in other tabs are activated.
I have used <%# OutputCache Duration="120" VaryByParam="none" %> within my user control. When the user logs in NullReferenceException is generated on one of the method within that control.
When I remove the OutputCache, everything works fine.
Could someone guide me what should i do?
Thanks in advance
The "easy" way to fix this is to check if the value is null, if it is null create it.
A better way would be to find out why it is null.
One possibility is that the first time that page is called there is a parameter that determines that one of the controlls should not be created. The second time it is called it is called with a parameter that say that the controll is required, but it is using a cached version of the page that does not have that controll.
Related
I have a asp.net webpage that displays a link Login or Logout depending on a session variable "IsLogged". I want to implement caching in that page. But after applying caching the Login/Logout becomes inconsistent with the session variable. What is the best approach to address this problem so that I can also apply caching in that page?
Thanks,
Partha
I am not sure how you are caching specifically but you could break your page up into two user controls (ascx).
Your aspx page could contain the user control to that shows the login information (make sure that when you load the user control with a dynamic url so that the caching ignores it because the address is diff everytime like:
yourSessionInfo.ascx?stopcache=32487239875 (the number could be just current time in ticks)
You just need something that changes in your url so that the page 'looks' like it is different and reloads.
Then have the rest of your page in another user control that has a static url:
yourRestOfPage.asx
Notice nothing changing in the url so page can be cached.
Not sure if this will solve your exact problem but it should at least start you down the right path.
I'm trying to describe it in as few steps as possible:
I have Page1.aspx with lot of controls, and Preview and Save button among those. I also have Page2.aspx that is the redirection target of a Preview Button click.
Since I need all the controls selections from Page1 to draw a preview on Page2 the redirection is done with setting Preview's PostBackUrl.
I also must have preview shown on a new tab or window so I used onClientClick="aspnetForm.target='_blank'" for Preview button definition.
Save button-click callback, after storing data to a database does redirection to some Page0.aspx (initial list of reports - the subject of the code)
Preview button works fine - a preview renders in a new tab, but when I go to the old tab and click on Save, I see from debugger, that firstly Page2.aspx(?) and secondly Page1.aspx are loaded. Then all the data is stored in the db, but though Page0 redirection is executed Page1.aspx stays loaded in the browser.
I have no idea what processes are behind this. Could one who knows give me an insight? Or if you consider my approach impossible to implement give some idea how to do the same?
If it's of importance, everything on the Page1 is located in an update panel.
Thank you very much for replying
In ASP.NET there are basically zero (0) circumstances in which you will ever send form data from one page to another. Although what exactly you are trying to accomplish is vague, you can consider some of the following:
Isolate unique operations/systems to a single page. If you have something like a User Profile, don't have three different aspx pages; just use a single page for the user or admin to manage that data / functions. Postback events are your friend.
Understand the difference between ViewState and traditional form data. I'm guessing that if you're trying to post form data from one page to another, you probably don't understand the point of ViewState. Using a single page to maintain temporary data that the user is currently working with is a great use for ViewState. If you want the data to appear on another page then you need to consider the data from the previous page as final and thus should be saved to a database or some other medium.
These are just some general guidelines because there is no exact answer to your problem without saying something generic like "You're doing it wrong." I would recommend starting by never again trying to post form data from one aspx page to another.
We have a site where all pages are output cached, i.e. the caching is on aspx-level with VaryByParam="*". Now there is a requirement to make a gallup control, i.e. a small "How is this site working for you?" and then when the user clicks an answer the results are shown.
The gallup is implemented as a usercontrol that is added to the master page so gallups can be added to any page to which a gallup is created in the cms. The problem is that output cache naturally caches all clicks so when user no 2 votes he sees the results that where calculated after the first vote on that alternative.
Now I'm trying to use cache substition. I added an asp:Substition tag where the user control used to be, load the control dynamically and render it (using this approach http://coderwall.com/p/4ajzqq). The problem is that the postbacks that voting triggers is never fired. Apparently the method that the substition control executes is loaded outside the page life cycle or too late.
Any ideas?
Regards,
Mathias
I solved this by skipping the substitution control and just used the user control as normal, so the gallup/question view was output cached. Then in the click handler for the answer alternatives I added
Response.Cache.SetNoServerCaching();
which exempted the results view from output cache and hence it was updated as it should.
It is also possible to use Response.Cache.SetNoServerCaching() in Global.asax, using VaryByCustom. It merely requires sensing in Global.asax whether the page is a post-back or not. Here is a code example.
I've built an asp website and i have the following issues:-
i'm using a master page in it and have defined two contentplaceholders one in head one in content, and i've specified the page title in the top most directive at the #page directive but the page title doesn't show up. I have to manually add a tag for it.
Secondly when i create a content page from a master page it creates it and when i rename it, it doesn't rename it's class. It remains _Default, thus every page was having an inherit to _default.
Most importantly
I'm using a page to enter and view data to the database. I've used a boolean called isadmin which i set according to credentials at page load. and i'm added a panel where it's visible property is set to Visible = '<%#IsAdmin %>'. It works properly when i run it through the visual studio environment but when i publish it and run it doesn't work and the panel just comes and stays there. Why is it happening? Any idea?
Thanks
The Visible problem is fixed as i had to enable windows authentication on the server. Awaiting answers for the other two issues. Thanks
Try to add a <head runat=server> to the master page. Only then ASP.net can "see" the tag and modify it
It is not that bad that several aspx-pages have identical class names. ASP.NET 2.0 started to process every page as its own compiling unit or so. Pages cannot see each other. There is a special directive to make pages see each other and instanciate or manipulate them. So it should not do much harm
Maybe you did not test this correctly and are mistaken that it DOES work in Visual Studio??? But in any case I would suggest that you move your logic into OnInit, then it runs much earlier. I think the control tree is build before Page.OnLoad. What you do is data binding, that might run only if DataBind is called, I'm not sure
Or use the safe way: Make IsAdmin a property so that it initializes itself on first call and caches the result in a variable
Regarding question #2 - add your content pages via Project -> Add New Item, and name it appropriately there. That way the naming is consistent and correct throughout.
Regarding #3, what HTML is output when you run it from the server?
your first issue can be solved by filling out the title part of the #Page directive in your .aspx pages. The master page will display that text in the browsers title bar.
and prob #2 should be solved by adding the files using the file add option in visual studio.
Is it possible to save ViewState information, e.g. to session, so that when you navigate away from the page it is persisted somehow? Then when you return to that page you can reload the view state and the choices you've made are preserved.
Background
I have two pages, a report page, where you can pick data, do some filtering and sorting etc. and a chart-page, where the data you picked from the report page can be presented in different ways, with different choices for presentation.
If the user has tested different presentations, simply using the back-button could mean quite a few clicks before the user's back at the report page. I'd like a direct link to the report page.
Using QueryString to save control states is not an option.
I can't customize the ViewState storage for the whole application.
Yes, it's possible to store the Viewstate in something like a database. You just need to implement one of the viewstate providers. See here for an example using the SqlViewStateProvider.
Edit: Just re-read your post, and saw that you said you couldn't customize how the viewstate is stored for the whole application. If that's the case, you might want to look into storing it in a session. Scott Hanselman discusses that here.
Your link could automatically navigate back the required number of pages using JavaScript. Look at window.history, if you can count the number of pages forward you can navigate back that many.
The ViewState is already designed to persist the state of the user controls. If your user has made a selection and that selection is processed server side with a full page postback the new state of the controls will be saved in the ViewState (hidden input __VIEWSTATE).
If your report is using AJAX and partial page postbacks then you won't get the ViewState on the page anyway.
Just to clarify, the SQLViewstateProvider is NOT an application wide implementation. You have to create a class which inherits from the System.Web.UI.Page object and overrides the Save And Load viewstate methods of the Parent Page class. For each page that you want the viewstate to be saved on server side you then have to inherit from your newly created Page Template (Which in turn inherits and overrides the System.WEb.UI.Page class).
So it is applied on a per-page basis, not on an application-wide basis.
HEADS UP: Some controls might contain some client-side javascript code which may reference the viewstate on client-side (duh). If the viewstate is now stored on server-side you will get a null-reference exception (for instance, clicking a commandfield in a gridview). I'm working on a workaround for this problem, but unfortunately I do not have any concrete solution as of yet.
This is a bad idea, just use querystrings. I would be interested to know why they are not an option.